Alloy sheet metal for fins of heat exchanger and process for preparation thereof

Abstract

According to the present invention, a metal sheet is prepared by subjecting an Al slab, containing at least one element capable of peritectic reaction with Al, such as Ti, Zr and Mo, the amount of the element incorporated in the slab being 0.05 to 0.4% by weight when one element is incorporated and when two or more elements are incorporated, the amount of at least one element incorporated therein being 0.05 to 0.4% by weight and the total amount of the elements incorporated being not higher than 0.5% by weight, to a soaking heat treatment, hot-rolling the slab and then cold-rolling the hot-rolled slab. According to the present invention, the properties required for such metal sheet, namely the strength and formability, can be remarkably improved, and by the hardening treatment, the adherence between fins and tubes can be improved and the heat transfer efficiency can be remarkably elevated in the heat exchangers. Thus, according to the present invention, practically applicable hard thin fins can be provided.

What is claimed as new and desired to be securd by letters patent of the United States is: 
     
       1. A process for the preparation of metal sheets for use in the formation of fins of heat exchangers having tube-penetrating holes formed therein by piercing, burling, ironing and flanging steps, which comprises the steps of: subjecting an Al slab, comprising at least one member from Ti, Zr, Mo, Cr, V, Hf, Ta, W, Nb, Tc and Re capable of peritectic reaction with Al, the amount of said element incorporated within said slab being 0.05 to 0.4% be weight when one element is incorporated therein, and when two or more elements are incorporated therein, the amount of at least one element incorporated therein is 0.05 to 0.4% by weihgt, and the total amount of said elements being incorporated therein is up to 0.5% by weight, and the Al slab further comprises at least one member selected from the group consisting of up to 0.25% by weight of Cu, up to 0.5% by weight of Mg, up to 0.5% by weight of Mn, up to 0.7% by weight of Fe, up to 0.002% by weight of Be, up to 0.1% by weight of B in the form of TiB 2  and up to 0.7% by weight of Si, to a soaking treatment, hot-rolling said slab, and cold-rolling said hot-rolled slab.   
     
     
       2. A metal sheet as set forth in claim 1, wherein: said Al slab is subjected to an intermediate annealing, at a temperature not initiating recrystallization, after said hot-rolling or during said cold-rolling.   
     
     
       3. A metal sheet as set forth in claim 1, wherein: said Al slab is subjected to a tempering annealing after said cold-rolling.   
     
     
       4. A metal sheet as set forth in claim 3, wherein: said tempering annealing is carried out at a temperature of at least 150° C. for a period of 1 to 6 hours.   
     
     
       5. A metal sheet as set forth in claim 1, wherein: said soaking heat treatment is carried out at a temperature of 350° to 630° C for a period of 1 to 48 hours.   
     
     
       6. A metal sheet as set forth in claim 1, wherein: the reduction ratio during said cold-rolling step is at least 20%.   
     
     
       7. A metal sheet as set forth in claim 6, wherein: the reduction ratio is preferably at least 70%.   
     
     
       8. A metal sheet for use in the formation of fins of a heat exchanger comprising: means defining tube-penetrating holes formed therein by piercing, burling, ironing and flanging steps, and   wherein said metal sheet is an Al slab, comprising at least one member selected from Ti, Zr, Mo, Cr, V, Hf, Ta, W, Nb, Tc and Re capable of peritectic reaction with Al, the amount of said element incorporated within said slab being 0.05 to 0.4% by weight when one element is incorporated therein, and when two or more elements are incorporated therein, the amount of at least one element incorporated therein is 0.05 to 0.4% by weight, and the total amount of said elements being incorporated therein is up to 0.5% by weight, and the Al slab further comprises at least one member selected from the group consisting of up to 0.25% by weight of Cu, up to 0.5% by weight of Mg, up to 0.5% by weight of Mn, up to 0.7% by weight of Fe, up to 0.002% by weight of Be, up to 0.1% by weight of B in the form of TiB 2  and up to 0.7% by weight of Si, which has been subjected to a soaking heat treatment, hot rolling, cold rolling, and a tempering annealing, at a temperature of at least 150° C without initiating recrystallization, after said cold-rolling.   
     
     
       9. A metal sheet as set forth in claim 8 wherein the element capable of peritectic reaction with Al is preferably one member selected from Ti, Zr and Mo. 
     
     
       10. A metal sheet as set forth in claim 8 wherein one element capable of peritectic reaction with Al is preferably incorporated in an amount of 0.1 to 0.2% by weight. 
     
     
       11. A metal sheet as set forth in claim 8 wherein the Al slab further comprises 0.5 to 2.0% by weight of Zn.